1. Field of the Invention
The present invention is related to secure storage of digital information. More specifically, the present invention is related to encryption and the encoding and decoding of digital information of, for example, an odometer.
2. Description of the Related Technology
With the advent of electronic odometers in vehicles, odometer fraud has become easier for educated criminals. Electric odometers store the odometer value in non-volatile memory, usually an EEPROM or similar device in order to ensure that the odometer value is preserved when the vehicle is switched off. The problem with the EEPROM is that it has a standard protocol interface that allows easy reading and writing to the EEPROM for someone educated in the electrical arts.
A typical prior art electric odometer is illustrated in FIG. 1. The odometer 10 is composed of a microcontroller 12 that is used for processing the value for a display device (not shown). The serial EEPROM 14 is used to store the odometer value which can be written to the EEPROM or read from the EEPROM by the microprocessor 12 via signal lines 17 and 19, respectively. As shown in FIG. 1, however, these signals could also be written/read via contacts 16 and 18, respectively.
There have been prior attempts to remedy the problems presented by electronic odometers. For example U.S. Pat. No. 5,924,057 disclosed a method of preventing odometer fraud employing a multiplex ring and a plurality of vehicle control modules. The odometer value was stored in the cluster control module and, periodically, in another module. If the main odometer value was tampered with, it would quickly be detected upon comparison with the value stored in an alternate module.
U.S. Pat. No. 5,297,178 discloses a tamper resistant system having a programmable memory counter with a plurality of memory locations arranged sequentially. Each of the memory locations includes a predetermined number of storage elements. Each storage element is programmable from a first value to a second value but not visa-versa. As these storage elements comprise the counter, the odometer reading of a vehicle cannot be reduced. Neither of these solutions, however, completely protects the odometer value, which is still subject to tampering, albeit with greater difficulty.
There is, therefore, a need in the art for a vehicle odometer that cannot be altered after initial setting. It is an object of the present invention to overcome the limitations inherent in the prior art.
The present invention solves the problems inherent in the prior art by providing a different vehicle odometer having an encoder in lieu of the standard EEPROM.
The encoder utilizes an encryption algorithm. The present invention will work with any encryption algorithm, the selection of which is left for the customer. According to one embodiment, when the encoder receives an increment signal, such as one generated when a vehicle travels a pre-determined distance, an odometer value is combined with another value to form a larger (longer) value that is harder to break. The larger bit value may then be encrypted by the encoder using the encryption algorithm and stored in the encoder""s own EEPROM. A microcontroller is used to receive the encrypted value from the encoder and then to decrypt it in real time for transmission to a display device.
Other and further objects, features and advantages will be apparent from the following description of presently preferred embodiments of the invention, given for the purpose of disclosure and taken in conjunction with the accompanying drawings.